Motor with backing ring diecast in rotor can

ABSTRACT

An electric fan includes a plurality of blades and an electric motor for rotating the blades. The electric motor includes a stator and a rotor rotatable relative to the stator about an axis. The rotor includes a backing ring and a diecast rotor can. The can includes a non-machined sidewall that is diecast integrally as part of the rotor can. The sidewall extends about the axis. The rotor can is diecast in an overlying relationship with at least part of the backing ring, with the sidewall and backing ring being securely interengaged so as to restrict relative shifting therebetween.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from U.S. Provisional PatentApplication No. 62/019,352, filed Jun. 30, 2014 (“the '352 provisionalapplication”), the entire disclosure of which is hereby incorporated byreference herein.

Furthermore, the '352 provisional application was filedcontemporaneously with U.S. Provisional Patent Application No.62/019,354, U.S. Provisional Patent Application No. 62/019,356, and U.S.Provisional Patent Application No. 62/019,357, the entire disclosures ofeach of which are hereby incorporated by reference herein. Yet further,the present application is being filed contemporaneously withnon-provisional applications claiming priority from respective ones ofthe aforementioned provisional applications.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to electric motors, which areparticularly suitable for use as part of a large fan. More particularly,the present invention concerns the rotor of the electric motor, whereinthe rotor includes a diecast rotor can and a magnetic backing ring castinto place during formation of the can.

2. Discussion of the Prior Art

In many motor applications, the rotor carries significant loads and mustconsequently have the structural integrity to operate in theseconditions. For example, some motor-driven fans (particularly fanshaving a diameter greater than one (1) meter) have fan blades supportedon the rotor. Such motors often have an outer rotor construction, withthe rotor can generally circumscribing the stator and supporting theblades.

The fabrication of a motor with a heavily loaded rotor is often timeconsuming and costly. More specifically, the rotor can is typicallyformed of metal and must be machined to facilitate precise mounting andsupport of the magnets and backing ring. The backing ring is also oftenmachined. In such conventional motor designs, the magnets and backingring must be appropriately secured to the can, typically with a precisepress-fit connection, fasteners, and/or adhesive.

Yet further, the foregoing prior art motor designs often requirebalancing of the rotor assembly (including any components, such as fanblades, carried by the rotor). For example, in large fans, dynamicbalancing of the rotor and blades can often be extremely time consuming(e.g., balancing operations can often exceed fifteen (15) minutes).

SUMMARY

According to one aspect of the present invention, an electric motor isprovided. The electric motor comprises a stator and a rotor rotatablerelative to the stator about an axis. The rotor includes a backing ringand a diecast rotor can. The can includes a non-machined sidewall thatis diecast integrally as part of the rotor can. The sidewall extendsabout the axis. The rotor can is diecast in an overlying relationshipwith at least part of the backing ring, with the sidewall and backingring being securely interengaged so as to restrict relative shiftingtherebetween.

According to another aspect of the present invention, an electric fan isprovided. The fan comprises a plurality of blades and an electric motorfor rotating the blades. The electric motor includes a stator and arotor rotatable relative to the stator about an axis. The rotor includesa backing ring and a diecast rotor can. The can includes a non-machinedsidewall that is diecast integrally as part of the rotor can. Thesidewall extends about the axis. The rotor can is diecast in anoverlying relationship with at least part of the backing ring, with thesidewall and backing ring being securely interengaged so as to restrictrelative shifting therebetween.

This summary is provided to introduce a selection of concepts in asimplified form. These concepts are further described below in thedetailed description of the preferred embodiments.

This summary is not intended to identify key features or essentialfeatures of the claimed subject matter, nor is it intended to be used tolimit the scope of the claimed subject matter.

Various other aspects and advantages of the present invention will beapparent from the following detailed description of the preferredembodiments and the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Preferred embodiments of the present invention are described in detailbelow with reference to the attached drawing figures, wherein:

FIG. 1 is a bottom perspective view of an electric fan constructed inaccordance with a first preferred embodiment of the present invention;

FIG. 2 is a bottom perspective view of the motor of the fan of FIG. 1;

FIG. 3 is a top perspective view of the motor of FIG. 2;

FIG. 4 is an exploded bottom perspective view of the motor of FIGS. 2and 3;

FIG. 5 is a top perspective view of a mold for overmolding the core ofthe stator of the motor of FIGS. 1-4, particularly illustrating the moldin a closed position;

FIG. 6 is an exploded top perspective view of the mold of FIG. 5 and thestator core of the motor of FIGS. 1-4;

FIG. 7 is an exploded bottom perspective view of the mold and statorcore of FIG. 6;

FIG. 8 is a cross-sectional perspective view of the mold and stator coreof FIGS. 5-7, in addition to the covering applied to the core during theovermolding process;

FIG. 9 is a bottom perspective view of the covering of FIG. 8;

FIG. 10 is a top perspective view of the covering of FIGS. 8 and 9;

FIG. 11 is a cross-sectional bottom perspective view of the covering ofFIGS. 8-10;

FIG. 12 is an enlarged, fragmentary cross-sectional bottom perspectiveview of the covering of FIGS. 8-11;

FIG. 13 is an enlarged, partially fragmented cross-sectional side viewof the mold and stator core, as depicted in FIGS. 5-8 and with variousparts of the mold being fragmented and/or cross-sectioned, particularlyillustrating the positioning of the pins relative to the stator core;

FIG. 14 is a top perspective view of a pin block of the mold of FIGS.5-8;

FIG. 15 is a bottom perspective view of the pin block of FIG. 14;

FIG. 16 is bottom perspective view of the rotor can of the motor ofFIGS. 2-4;

FIG. 17 is a cross-sectional side view of the rotor can of FIG. 16;

FIG. 18 is a bottom view of a portion of the motor of FIGS. 2-4,particularly illustrating the relative positioning of the rotor and thestator;

FIG. 19 is a cross-sectional side view taken along line 19-19 of FIG.18;

FIG. 19a is an enlarged, fragmentary cross-sectional side view of aportion of the motor as shown in FIG. 19, particularly illustrating theaxial height of one of the coils;

FIG. 20 is a schematic view of the motor of FIGS. 2-4;

FIG. 21 is a schematic view of the high-efficiency power supply of FIG.20;

FIG. 22 is a circuitry schematic view of the high-efficiency powersupply of FIGS. 20 and 21; and

FIG. 23 is a table providing test data for a motor suitable for use inthe preferred fan embodiment of the present invention.

The drawing figures do not limit the present invention to the specificembodiments disclosed and described herein. The drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the preferred embodiments.

Furthermore, directional references (e.g., top, bottom, front, back, up,down, etc.) are used herein solely for the sake of convenience andshould be understood only in relation to each other. For instance, acomponent might in practice be oriented such that faces referred to as“top” and “bottom” are sideways, angled, inverted, etc. relative to thechosen frame of reference.

It is also noted that, as used herein, the terms axial, axially, andvariations thereof mean the defined element has at least somedirectional component along or parallel to the axis. These terms shouldnot be limited to mean that the element extends only or purely along orparallel to the axis. For example, the element may be oriented at aforty-five degree (45°) angle relative to the axis but, because theelement extends at least in part along the axis, it should still beconsidered axial. Similarly, the terms radial, radially, and variationsthereof shall be interpreted to mean the element has at least somedirectional component in the radial direction relative to the axis.

It is further noted that the term annular shall be interpreted to meanthat the referenced object extends around a central opening so as to begenerally toroidal or ring-shaped. It is not necessary for the object tobe circular, nor does the object have to be continuous. Similarly, theterm toroidal shall not be interpreted to mean that the object must becircular or continuous.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is susceptible of embodiment in many differentforms. While the drawings illustrate, and the specification describes,certain preferred embodiments of the invention, it is to be understoodthat such disclosure is by way of example only. There is no intent tolimit the principles of the present invention to the particulardisclosed embodiments.

Fan

With initial reference to FIG. 1, a machine 10 is provided. The machine10 preferably comprises an electric fan 12. The fan 12 is preferably aceiling fan for circulating air. Furthermore, the fan 12 is preferablysuitable for indoor and/or outdoor use. In a preferred embodiment, bothcommercial and residential uses are permissible. It is permissibleaccording to some aspects of the present invention, however, for the fanto be of an alternative type or to be intended solely for indoor use,residential use, etc.

The fan 12 preferably includes a motor 14 and plurality of airfoils orblades 16 driven by the motor 14 to cooperatively rotate about an axis.As shown in FIG. 1, the blades 16 are preferably evenly arcuately spacedapart about the axis, although alternative blade arrangements arepermissible without departing from the scope of the present invention.In a preferred embodiment, three (3) blades 16 are provided. The blades16 collectively rotate during operation of the motor 14 to thereby moveair.

In a preferred embodiment, the fan 12 is operable at speeds up toapproximately two hundred five (205) revolutions per minute (rpm). Moreparticularly, at a low speed setting, the fan 12 preferably operates atabout thirty-five (35) rpm. At a high speed setting, the fan 12preferably operates at about two hundred two (202) rpm. It ispermissible, however, for the fan to have a varying operating range andvarying low- and high-speed settings.

Preferably, the fan has an outer diameter of at least about one (1.0)meter (m). More preferably, the outer diameter of the fan 12 isapproximately one and twenty-five hundredths (1.25) m to approximatelyone and seventy-five hundredths (1.75) m. Most preferably, the fan outerdiameter is about one and five tenths (1.5) m. The tips of the blades 16preferably cooperatively define the outer diameter. Varying fan sizesare permissible according to some aspects of the present invention,however.

In a preferred embodiment, the fan 12 has an axial height (i.e., a drop)ranging from about two hundred twenty-five (225) millimeters (mm) toabout two thousand 2000 mm. Although variations in axial height arepermissible according to some aspects of the present invention, it istypically most desirable for the fan 12 to have a low vertical profile.

The fan 12 preferably weighs from about five and five tenths (5.5)kilograms (kg) to about seven and one half (7.5) kg. However, variationsin weight are permissible according to some aspects of the presentinvention.

The fan 12 preferably operates off of one hundred to two hundred forty(100-240) volts alternating current (VAC) at fifty to sixty (50-60)Hertz (Hz). Most preferably, the fan 12 includes a converter (not shown)that converts the one hundred to two hundred forty (100-240) VAC totwelve to twenty-four (12-24) volts direct current (VDC).

At high speed, the fan 12 preferably generates from about four thousand(4,000) cubic feet per minute (CFM) of airflow to about five thousand,five hundred (5,500) CFM. Most preferably, the fan generates about fivethousand, three hundred fifty (5,350) CFM of airflow at high speed.Greater or lesser air moving capabilities are permissible according tosome aspects of the present invention, however.

The fan 12 may suitably incorporate a variety of sensors, including butnot limited to infrared motion sensors, ambient light sensors, andenvironmental sensors (e.g., temperature and humidity sensors). Awireless Internet chip might be embedded, and/or a predictive learningmicroprocessor might be included.

The motor 14 preferably includes a stator 18 and a rotor 20 rotatablerelative to the stator 18 about the axis. As will be discussed ingreater detail below, portions of the rotor 20 preferably at leastsubstantially circumscribe the stator 18, such that the motor 14 is anouter rotor motor. It is permissible according to some aspects of thepresent invention, however, for an inner rotor motor, a dual rotormotor, or an otherwise alternatively configured motor to be used.

In a preferred embodiment, the motor 14 defines at least ten (10) poles.More preferably, the motor 14 defines sixteen (16) to twenty-four (24)poles. Most preferably, the motor 14 defines twenty (20) poles.

In a preferred embodiment, the motor 14 preferably has a nine (9) slotto ten (10) pole ratio. Most preferably, the motor has eighteen (18)slots and twenty (20) poles. However, it is permissible according tosome aspects of the present invention for an alternative slot-to-poleratio to be provided (e.g., in association with one of the permissiblealternative numbers of poles discussed above).

As will be discussed in greater detail below, the rotor 20 preferablyincludes a rotor can 22, a backing ring 24 fixed relative to the can 22,and a plurality of arcuately arranged magnets 26 fixed relative to thecan 22 and the backing ring 24.

As will be discussed in greater detail below, the stator 18 preferablyincludes a core 28, an electrically insulative covering 30 formed aboutthe core 28, and a plurality of coils 32 wound about the core 28. It ispermissible according to some aspects of the present invention, however,for alternatively configured insulation or even no insulation to beprovided. For instance, according to some aspects of the presentinvention, the stator core 28 might alternatively be provided withelectrically insulative powder-coating.

The motor 14 also preferably includes a shaft 34 on which the rotor 20is rotatably supported by a bearing assembly 36. The bearing assembly 36may be of any type suitable for the particular application. In apreferred embodiment, as illustrated, the bearing assembly 36 includes apair of ball bearings 38.

The rotor 20 is preferably rotatable about an axis at least in partdefined by the shaft 34. However, an alternative rotation axis ispermissible according to some aspects of the present invention. Forinstance, the rotation axis might at least in part be parallel to butradially offset from the shaft axis.

For clarity and brevity, the direction of the shaft 34 extensionrelative to the remainder of the motor 14 will be described as beingupward. Other directional references used herein will be based on thisframe of reference. As noted previously, however, directional referencesused herein should understood only in relation to each other and are notnecessarily applicable relative to the broader environment in which theinvention is operable.

Rotor

The rotor can 22 preferably includes a generally radially extending baseplate 40 and a sidewall 42 extending axially from the base plate 40 andarcuately about the axis. The illustrated sidewall 42 is continuous andcircular in shape. However, with respect to certain aspects of thepresent invention, the sidewall can alternatively comprise spaced apartsegments or have alternative shapes (although symmetry about the rotoraxis is preferred). Furthermore, the sidewall may alternatively extendat a different angle from the base plate. Those of ordinary skill in theart will appreciate that the base plate may similarly be alternativelyconfigured without departing from the spirit of the present invention.Preferably, the sidewall 42 extends at least generally upwardly from thebase plate 40.

As will be discussed in greater detail below, the backing ring 24 ispreferably fixed relative to the sidewall 42, while the magnets 26 arefixed relative to the backing ring 24. Furthermore, in a preferred outerrotor motor embodiment, the backing ring 24 is at least substantiallypositioned radially inwardly relative to the sidewall 42, while themagnets 26 are at least substantially positioned radially inwardlyrelative to the backing ring 24.

As best shown in FIGS. 2 and 4, the rotor 20 preferably further includesa stator cover 44 that is preferably attached to the can 22 via statorcover bosses 46 and stator cover fasteners 48. It is permissible,however, for the stator cover to be omitted or to be attached byalternative means, such as adhesives and/or latches.

As best shown in FIG. 19, the stator cover 44, the can 22, and themagnets 26 preferably cooperatively in part define a generallycylindrical stator compartment 50. The stator 18 is at leastsubstantially received in the stator compartment 50.

The sidewall 42 preferably defines axially spaced apart upper and lowermargins 52 and 54. The upper margin 52 is preferably adjacent the baseplate 40, while the lower margin 54 preferably defines the lowermostedge of the can 22.

The upper margin 52 and the lower margin 54 are preferably spaced aparta distance that may be referred to as the axial height of the sidewall42. The axial height of the sidewall 42 is preferably less than aboutforty-five (45) mm. More preferably, the axial height of the sidewall 42is from approximately thirty (30) mm to approximately forty (40) mm.Most preferably, the axial height of the sidewall 42 is aboutthirty-five (35) mm.

In a preferred embodiment, the axial height of the stator compartment 50is at least substantially equal to the axial height of the sidewall 42.

The backing ring 24 and the rotor can 22 are preferably generallyannular or toroidal in shape, respectively, while the sidewall 42preferably extends at least substantially arcuately to have an at leastsubstantially toroidal shape. More preferably, the backing ring 24 andthe rotor can 22 are preferably circular in shape, with the sidewall 42extending at least substantially circumferentially.

As noted previously, the sidewall 42 preferably extends at leastsubstantially continuously and most preferably extends entirelycontinuously. It is permissible according to some aspects of the presentinvention, however, for the sidewall to be segmented, perforated, orotherwise discontinuous.

The can 22 preferably has an outer diameter defined by the sidewall 42.More particularly, the sidewall 42 preferably defines an inner sidewallface 56 and an outer sidewall face 58. The outer sidewall face 58defines the outer diameter of the can 22. The outer diameter of the can22 (and thus the sidewall 42) is preferably less than about two hundredfifty (250) mm. More preferably, the outer diameter of the can 22 (andthus the sidewall 42) is from approximately one hundred sixty (160) mmto approximately two hundred (200) mm. Most preferably, the outerdiameter of the can 22 (and thus the sidewall 42) is about one hundredeighty-five (185) mm.

The inner sidewall face 56 and the outer sidewall face 58 are preferablyparallel and preferably both extend at least substantially axially. Itis permissible according to some aspects of the present invention,however, for the faces to be non-parallel and/or non-axially extending.

As shown in FIG. 16 and others, the backing ring 24 preferably defines apair of axially spaced apart upper and lower backing ring faces 60 and62 (i.e., a pair of end faces), respectively, that project at leastgenerally outwardly relative to the axis. Furthermore, the backing ring24 preferably defines an inner backing ring face 64 and an outer backingring face 66 (i.e., a pair of side faces).

The inner and outer backing ring faces 64 and 66 are preferably radiallyspaced apart and generally oppositely directed. The inner and outerbacking ring faces 64 and 66 also preferably extend axially from andinterconnect the upper and lower backing ring faces 60 and 62. In apreferred embodiment, the upper and lower backing ring faces 60 and 62are preferably planar, parallel with each other, and at leastsubstantially orthogonal to the axis. The upper and lower backing ringfaces 60 and 62 therefore are not only non-parallel with the inner andouter backing ring faces 64 and 66, but also at least substantiallyorthogonal thereto. It is permissible according to some aspects of thepresent invention, however, for the faces of the backing ring to bealternatively oriented relative to each other.

As noted previously and as best shown in FIGS. 4 and 19, the magnets 26are preferably evenly arcuately arranged and are fixed relative to thebacking ring 24. It is permissible, however, for the magnets to beunevenly and/or non-arcuately arranged.

In a preferred embodiment, the magnets 26 are fixed to one of the innerand outer backing ring faces 64 and 66. As noted above, the motor 14 ismost preferably an outer rotor motor, with the magnets 26 being mountedto the inner backing ring face 64 and with the backing ring 24 and themagnets 26 at least substantially circumscribing the stator 18.

The magnets 26 are preferably adhered to the backing ring 24, althoughany one or more of a variety of mounting means may be used withoutdeparting from the scope of the present invention.

In a preferred embodiment, ten (10) magnets 26 are provided andconfigured in such a manner that the motor has (20) poles. It ispermissible according to some aspects of the present invention, however,for more or fewer magnets to be provided.

Each magnet 26 preferably has a radial depth from about three (3) mm toabout seven (7) mm and an arcuate length from about eighteen (18) mm toabout twenty-two (22) mm. Most preferably, each magnet 26 has a radialdepth of about five (5) mm and a radial length of about twenty (20) mm.

The magnets 26 preferably cooperatively define a rotor inner margin 68.The rotor inner margin 28 preferably defines a inner diameter of therotor 20 that is less than about two hundred (200) mm. More preferably,the inner diameter of the rotor 20 is from about one hundred sixty (160)mm to about one hundred seventy-five (175) mm. Most preferably, theinner diameter of the rotor 20 is approximately one hundred sixty-four(164) mm.

The magnets 26 also cooperate with the stator 18 to define the air gapfor the motor, as will be described in greater detail below.

The magnets 26 are preferably permanent magnets. More preferably, themagnets 26 are ferrite permanent magnets. Most preferably, the magnets26 are grade six (6) ferrite permanent magnets. It is permissibleaccording to some aspects of the present invention, however, for themagnet type to vary.

In a preferred embodiment, the blades 16 are mounted to the can 22. Moreparticularly, the can 22 preferably includes a plurality of mountingflanges 70 on which the blades 16 are mounted. Preferably, the number ofmounting flanges 70 is equal to the number of blades 16. Mostpreferably, therefore, three (3) mounting flanges 70 are provided.

The mounting flanges 70 each preferably extend generally radiallyoutwardly from the sidewall 42. Furthermore, the mounting flanges 70 arepreferably evenly arcuately spaced apart.

The can 22 preferably includes a bearing housing 72 that defines abearing pocket 72 a that at least in part receives the bearings 38 ofthe bearing assembly 36. The pocket 72 a and the backing ring 24 arepreferably at least substantially concentric.

Furthermore, the can 22, the backing ring 24, the magnets 26, and theblades 16 are preferably collectively at least substantiallyrotationally symmetrical and at least substantially rotationallybalanced.

In a preferred embodiment, the can 22 is diecast of a metal material,with the base plate 40, the sidewall 42, and the mounting flanges 70being integrally formed.

Again, the sidewall 42 is preferably diecast integrally as part of thecan 22. Furthermore, sidewall 42 is preferably non-machined (e.g., nomachining occurs to the sidewall after is it cast in the diecastingprocess).

The can 22 is preferably diecast in an overlying relationship with atleast part of the backing ring 24, with the sidewall 42 and the backingring 24 thereby being securely interengaged so as to restrict relativeshifting therebetween. Preferably, the motor 14 is devoid of fasteners,adhesives, welds, or other means for interconnecting the backing ring 24and the can 22. That is, the backing ring 24 is secured in the can 22only as a result of the diecasting process.

More particularly, as best shown in FIGS. 16, 17, and 19, the sidewall42 preferably includes an upper non-machined, diecast shoulder portion74 and a lower non-machined, diecast shoulder portion 76 spaced axiallyfrom the upper shoulder portion 74. The upper shoulder portion 74preferably abuts the upper backing ring face 60, while the lowershoulder portion 76 preferably abuts the lower backing ring face 62. Theshoulder portions 74 and 76 thereby axially capture the backing ring 24therebetween.

The sidewall 42 also preferably includes anon-machined, diecast axialportion 78 that extends between the shoulder portions 74 and 76 andabuts one of the inner and outer backing ring faces 64 and 66. In thepreferred outer rotor embodiment of the motor 14, the axial portion 78abuts the outer backing ring face 66 and is defined by the innersidewall face 56.

Preferably, the one of the inner and outer backing ring faces 64 and 66that abuttingly engages the sidewall 42 (and does not support themagnets 26) is devoid of machining. The other of the inner and outerbacking ring faces 64 and 66, however, may be machined if desired. Moreparticularly, in a preferred embodiment, the outer backing ring face 66is non-machined, while the inner backing ring face 64 is machined.

The sidewall 42 further preferably includes an inner shoulder portion 80spaced radially inwardly and axially upwardly from the upper shoulderportion 74. The inner shoulder portion 80 is preferably machined afterdiecasting of the can 22, although it is permissible for the innershoulder portion to alternatively be non-machined.

As best shown in FIGS. 17 and 19, an annular groove 82 is preferablyformed between the upper and inner shoulders 74 and 80, respectively.The groove 82 enables the elimination of a radius that would otherwisebe formed between the upper shoulder 74 and the inner shoulder 80. Insome cases, the groove 82 may also receive excess glue from the magnetadhesion process.

In a preferred embodiment, the can 22 comprises aluminum. It ispermissible according to some aspects of the present invention, however,for the can to comprise one or more alternative materials, although suchmaterials are limited in cases in which the preferred diecasting processis used. If the can is instead molded, for instance, plastic might beused.

In the case of a diecast can 22, it is noted that it is particularlyimportant that the backing ring 24 have a sufficient radial thickness(i.e., the radial distance between the inner and outer backing ringfaces 64 and 66) to withstand the heat associated with the diecastingprocess without problematic degrees of expansion and/or other forms ofdeformation. For instance, the heat of the molten aluminum of the can 22in a preferred diecasting process necessitates that the backing ring 24have a radial thickness of approximately two (2) mm to approximatelyfour (4) mm. Most preferably, the backing ring 24 has a radial thicknessof about three (3) mm.

The can 22 and the backing ring 24 preferably comprise dissimilarmaterials. More particularly, as noted above, the can 22 preferablycomprises aluminum, while the backing ring 24 preferably comprises steelor any other suitable magnetic material.

Those of ordinary skill in the art will recognize that theabove-described diecasting approach to securing of the backing ring 24in the rotor can 22 is highly advantageous, enabling secondary machiningand pressing operations conventionally necessary for insertion of abacking ring into a can (e.g., machining of the sidewall of the can andthe outer face of the backing ring, followed by pressing of the backingring into the machined opening) to be eliminated without loss of theconcentricity of the backing ring 24 and the bearing pocket 72 a. Amongother things, such concentricity is necessary for balance, radialuniformity of the air gap (to be discussed in greater detail below)between the rotor 20 and the stator 18, optimal sound response, andmotor performance in general.

It is also particularly noted that the principles of diecasting abacking ring into a rotor can are applicable to motors in a variety ofapplications distinct from electric fans. Among other things, forinstance, a diecast rotor can as described above could suitably be usedin appliances such as washing machines or in exercise equipment such aselectric bicycles or bicycle generators.

Stator

As noted previously, the motor 14 preferably includes a stator 18 and arotor 20. As also noted previously, the stator 18 is preferably aninsulated stator and includes a core 28, an electrically insulativecovering 30 formed on the core 28, and a plurality of coils 32 woundabout the core 28.

In a preferred embodiment, the stator 18 is preferably generallytoroidal in form. The core 28 is likewise preferably generally toroidalin form and defines an axis of the stator 18. Preferably, the axis ofthe stator 18 is coaxial with that of the rotor 20. However, it ispermissible according to some aspects of the present invention for theaxes to be non-coaxial.

As noted previously and as best shown in FIGS. 18 and 19, the stator 18is preferably at least substantially received in the stator compartment50.

The core 28 preferably includes an annular yoke 84 and a plurality ofarcuately spaced apart teeth 86 extending at least generally radiallyfrom the yoke 84. Preferably, the teeth 86 extend radially outwardlyfrom the yoke 84 (because of the preferred outer rotor motor design),although it is permissible according to some aspects of the presentinvention for the teeth to extend generally inwardly.

Each tooth 86 preferably includes a generally radially extending arm 88and a generally arcuately extending crown 90 extending from one end ofthe arm 88. Each crown 90 preferably defines a pair of arcuately spacedapart tips 92. The tips 92 are preferably spaced apart by an arcuatedistance of between about two (2) mm and about five (5) mm. Mostpreferably, the tips 92 are spaced apart about three and five tenths(3.5) mm.

Each crown 90 further preferably presents a circumferential crown face94 spaced opposite the yoke 84. The circumferential crown faces 94preferably cooperatively define a first radial margin 96 of the core 28.Again, because the illustrated motor 14 has an outer rotor design, thecircumferential crown faces 94 are preferably outer circumferentialfaces, such that the first radial margin 96 is a radially outermostmargin.

The yoke 84 preferably presents an inner circumferential yoke face 98and an outer circumferential yoke face 100. One of the inner and outercircumferential yoke faces 98 and 100 preferably defines a second radialmargin 102 of the core 28. Preferably, the inner circumferential yokeface 98 defines the second radial margin 102 of the core 28, such thatthe second radial margin 102 is a radially innermost margin. In such anembodiment, it will be readily apparent of one of ordinary skill in theart that the outer circumferential yoke face 100 is discontinuous due tothe teeth 86 extending therefrom.

The core 28 preferably has an outer diameter defined by the first radialmargin 96. The outer diameter of the core 28 is preferably less thanabout two hundred (200) mm. More preferably, the outer diameter of thecore 28 is from approximately one hundred sixty (160) mm toapproximately one hundred seventy-five (175) mm. Most preferably, theouter diameter of the core 28 is approximately one hundred sixty-two andfive tenths (162.5) mm. As will be further described, the covering 30does not overlie the faces 94 of the teeth 86, and the outer corediameter consequently defines the outer diameter of the illustratedstator 18.

The core 28 preferably has an inner diameter defined by the secondradial margin 102. The inner diameter of the core 28 is preferably lessthan about one hundred thirty (130) mm. More preferably, the innerdiameter of the core 28 is from approximately ninety (90) mm toapproximately one hundred ten (110) mm. Most preferably, the innerdiameter of the core 28 is approximately one ninety-six and five tenths(96.5) mm.

As noted previously, the rotor 20 preferably at least substantiallycircumscribes the stator 18. More particularly, as best shown in FIGS.18 and 19, each of the magnets 26 is preferably spaced radiallyoutwardly from the first radial margin 96 of the core 28, such that thecore 28 and the magnets 26 cooperatively define a circumferentiallyextending gap 104 therebetween. (That is, the inner diameter of therotor 20 is preferably slightly larger than the outer diameter of thecore 28.)

The gap 104 is preferably about one and five tenths (1.5) mm in radialthickness, in keeping with the aforementioned most preferred rotor 20inner diameter of about one hundred sixty-four (164) mm and theaforementioned most preferred core 28 outer diameter of about onehundred sixty-two and five tenths (162.5) mm. However, the gap thicknessmay vary without departing from the scope of some aspects of the presentinvention.

Preferably, the yoke 84 and the teeth 86 cooperatively further presentopposite axial end faces 106 and 108. The end faces 106 and 108 arepreferably at least substantially planar and parallel with each other,although non-parallel and/or non-planar surfaces are permissibleaccording to some aspects of the present invention.

The core 28 preferably has an axial height (i.e., a stack height)defined as the axial distance between the end faces 106 and 108. Theaxial height of the core 28 is preferably less than about twenty-five(25) mm. More preferably, the axial height of the core 28 is fromapproximately twelve (12) mm to approximately eighteen (18) mm. Mostpreferably, the core 28 has an axial height of about fifteen (15) mm.

Preferably, the teeth 86 each present a pair of side faces 110 extendingbetween and interconnecting the upper and lower end faces 106 and 108.Each side face 110 projects generally radially between the outer yokeface 100 and the outer circumferential face 94 of the tooth 86. Eachside face 110 consequently presents an arm portion 112 and a crownportion 114.

As best shown in FIG. 18, adjacent side faces 110 of each adjacent pairof teeth 86 preferably define a slot 116 therebetween. Preferably, thecore 28 includes twenty (20) teeth 86 such that, as noted previously,twenty (20) slots 116 are defined.

The coils 32 preferably comprise electrically conductive wiring 118. Thewiring 118 is preferably wound about each of the teeth 86 through theslots 116 to form the coils 32, with each of the coils 32 correspondingto one of the teeth 86.

Each of the coils 32 preferably comprises twenty-five (25) to fifty (50)turns of the wiring 118. More preferably, each of the coils 32 comprisesthirty (30) to forty (40) turns of the wiring 118. Most preferably, eachcoil 118 comprises thirty-one (31) turns of the wiring 118.

The wiring 118 preferably forms as many as three (3) layers. Mostpreferably, however, and as shown in FIGS. 19 and 19 a, the wiring 118forms two (2) layers.

The wiring 118 preferably comprises copper, although aluminum or any ofa variety of electrically conductive materials may be used withoutdeparting from the scope of some aspects of the present invention.

The wiring 118 preferably has a gauge from about eighteen (#18.0) toabout nineteen and five tenths (#19.5). Most preferably, however, thewire is eighteen and five tenths gauge (#18.5) wire.

Each of the coils 32 preferably has a total axial height of less thanabout thirty (30) mm. More preferably, each of the coils 32 preferablyhas an axial height from approximately eighteen (18) mm to approximatelytwenty-three (23) mm. Most preferably, each of the coils 32 preferablyhas an axial height of approximately twenty-one (21) mm.

As shown in FIG. 19a , the layers of wiring 118 preferably present anaggregate axial height or coil thickness t of the coils 32 (i.e., anaxial height beyond the respective axial end face 106 or 108 of the core28 and the associated covering 30) of at most about five (5) mm. Morepreferably, the coils 32 have a thickness t of about one (1) mm to aboutthree (3) mm. Most preferably, the coils 32 have a thickness t of about(1) mm to approximately two (2) mm. Such thickness t is preferablypresented cooperatively by two (2) layers of wiring 118, as discussedabove, although other numbers of layers may in some embodiments presentthe overall coil thickness.

In view of the above, it will be readily apparent to one of ordinaryskill in the art that the coils 32 add at most about ten (10) mm to theoverall stator height, more preferably from about two (2) mm to aboutsix (6) mm to the overall stator height, and most preferably about two(2) mm to about four (4) mm to the overall stator height.

The core 28 is preferably a laminated core. The laminations arepreferably about seven hundred eighty seven thousandths (0.787) mmthick. However, it is permissible for the core to be a solid core or tohave different lamination thicknesses without departing from the scopeof the present invention.

The core 28 preferably comprises steel. More particularly, the corepreferably comprises S85H5 steel. However, it is permissible withoutdeparting from the scope of some aspects of the present invention forany one or more of a variety of materials to be used for the core.

The covering 30 preferably comprises a synthetic resin material, but anyone or more of a variety of substantially electrically insulativematerials may be used without departing from the scope of the presentinvention.

The covering 30 preferably includes a yoke portion 120 covering at leastpart of the yoke 84 and a plurality of arcuately spaced apart toothportions 122 each corresponding with and at least in part covering oneof the teeth 86. Preferably, the covering 30 includes a tooth portion122 for each tooth 86. That is, the number of tooth portions 122 and thenumber of teeth 86 is preferably the same, with each tooth 86 preferablybeing provided with electrical insulation via the covering 30. It ispermissible according to some aspects of the present invention, however,for some of the teeth to not be covered by the covering.

In a preferred embodiment, the upper and lower end faces 106 and 108 ofthe core 28 are preferably at least substantially covered by thecovering 30, both adjacent the teeth 86 and adjacent the yoke 84. Theside faces 110 of the teeth 86 and the inner and outer circumferentialyoke faces 98 and 100 are also preferably at least substantially coveredby the covering 30. Preferably, the side faces 110 and the inner andouter circumferential yoke faces 98 and 100 are entirely covered by thecovering 30.

However, the circumferential crown faces 94 of the teeth 86 and thus thefirst radial margin 96 of the core 28 are at least substantially devoidof the covering 30.

The wiring 118 is preferably wound about the teeth 86 on the outside ofthe tooth portions 122 of the covering 30, such that the wiring 118 isnot in direct contact with the core 28 itself. That is, the covering 30preferably insulates the core 28 from the wiring 118.

The yoke portion 120 of the covering 30 preferably includes an upperyoke-covering portion 124 and a lower yoke-covering portion 126 spacedaxially from the upper yoke-covering portion 124.

Each of the tooth portions 122 of the covering 30 preferably includes anupper tooth-covering portion 128 and a lower tooth-covering portion 130spaced axially from the upper tooth-covering portion 128.

Each of the upper tooth-covering portions 128 of the covering 30preferably includes an upper tooth opening 132 extending through thecovering 30 to a respective one of the teeth 86 to expose the core 28.Similarly, each of the lower tooth-covering portions 130 preferablyincludes a lower tooth opening 134 extending through the covering 30 toa respective one of the teeth 86 to further expose the core 28. That is,the tooth 86 is not covered by the covering 30 at the tooth openings 132and 134.

The upper and lower tooth openings 132 and 134 preferably form alignedpairs and are preferably defined along respective ones of the upper andlower end faces 106 and 108 of the core 28 adjacent the teeth 86. It ispermissible according to some aspects of the present invention, however,for the tooth openings to be non-aligned, non-paired, and/oralternatively positioned. For instance, each tooth portion might defineonly one of the upper and lower tooth openings rather than a pair, aspreferred. Yet further, some of the tooth portions might be entirelydevoid of tooth openings.

Regardless of whether all or only some of the tooth portions includetooth openings and regardless of whether each tooth portion thatincludes an a tooth opening includes both upper and lower tooth openings(rather than just one opening), it is preferred that the tooth openingsbe arranged rotationally symmetrically. For instance, every other toothmight include both upper and lower tooth openings, or only upper toothopenings might be found on a first set of teeth that are arcuatelyoffset by one tooth from a second set of teeth on which only lower toothopenings are found. Irregular spacing is permissible according to someaspects of the present invention.

In a preferred embodiment, the upper and lower tooth openings 132 and134, respectively, are positioned at least substantially adjacent thefirst radial margin 96 of the core 28. Alternative positioning ispermissible according to some aspects of the present invention, however.

Furthermore, each of the upper and lower tooth openings 132 and 134preferably comprises a notch 136. The notch 136 preferably takes agenerally semicircular shape. It is within the ambit of the presentinvention, however, for the upper and lower tooth openings to be in analternate form or for the notch to be of another shape, such astriangular or rectangular.

In a preferred embodiment, the yoke portion 120 of the covering 30defines upper and lower sets of yoke holes 138 and 140, respectively,extending through the covering 30 such that a portion of the core 28 isexposed at the yoke holes 138 and 140. The upper yoke holes 138 arepreferably defined by the upper yoke-covering portion 124 along theupper end face 106 of the core 28, while the lower yoke holes 140 arepreferably defined by the lower yoke-covering portion 126 along thelower end face 108 of the core 28.

The upper yoke holes 138 are preferably evenly arcuately spaced apart,and the lower yoke holes 140 are likewise preferably evenly arcuatelyspaced apart. Furthermore, the upper yoke holes 138 are preferablyaligned with corresponding ones of the lower yoke holes 140.

In a preferred embodiment, six (6) upper yoke holes 138 and six (6)lower yoke holes 140 are provided.

Preferably, the yoke 84 defines a plurality of yoke openings 142, eachof which is aligned with one of the upper yoke holes 138 and one of thelower yoke holes 140. As best seen in FIG. 19, the yoke openings 142preferably have a smaller diameter than the upper and lower yoke holes138 and 140, thereby enabling exposure of a portion of the correspondingend faces 106 and 108, in addition to the portion of the interior of thecore 28 defining the corresponding yoke opening 142.

The yoke openings 142 preferably extend at least substantially axially,with the upper and lower yoke holes 138 and 140 being axially andarcuately aligned with the yoke openings 142.

The tooth portions 122 and the yoke portion 120 are preferablyintegrally formed with each other, as will be discussed in greaterdetail below. More particularly, the tooth portions 122 and the yokeportion 120 are preferably integrally overmolded over the core 28.

In a preferred embodiment, as best shown in FIGS. 6 and 7, each of theteeth 86 further includes an axially extending tooth slit 144 extendingtherethrough. Preferably, each tooth slit 144 is positioned adjacent theinterface between the arm 88 and the crown 90 of the respective tooth86.

The covering 30 preferably includes a plurality of tooth pillars 146corresponding to and extending through the tooth slits 144.

In a preferred embodiment, as best shown in FIGS. 6 and 7, the yoke 84further includes a plurality of axially extending yoke slits 148extending therethrough. Preferably, the yoke slits 148 are evenlyarcuately arranged. More particularly, each yoke slit 148 is preferablypositioned in radial alignment with a corresponding one of the slots 116defined by the teeth 86.

The covering 30 preferably includes a plurality of yoke pillars 150corresponding to and extending through the yoke slits 148.

As best shown in FIGS. 2 and 4, the covering 30 also preferably definesan electronics compartment 152 that receives motor electronics 154therein. More particularly, the covering 30 preferably includes acentral body portion 155 including a generally circumferential wall 155a and a generally radially extending base 155 b from which the wall 155a extends. The wall 155 a and the base 155 b cooperatively at least inpart define the electronics compartment 152.

In a preferred embodiment, as illustrated, the motor electronics 154include a motor control including a printed circuit board 154 a andvarious electronic components 154 b mounted to the board 154 a. Moreparticularly, the covering 30 presents a plurality of arcuately spacedapart electronics bosses 156, each of which defines an electronicsfastener-receiving opening 158 that receives an electronics fastener 160that secures the board 154 a to the stator 18. In a preferredembodiment, four (4) electronics bosses 156 are provided, although moreor fewer are permissible without departing from the scope of the presentinvention.

The covering 30 also preferably defines a mounting flange 162connectable to a structure such that the covering 30 is operable tosupport the core 28 on the structure or, alternatively, to support thestructure on the core. For instance, an electronics compartment cover(not shown but preferably provided) might be mounted on the mountingflange 162.

The mounting flange 162 preferably presents a plurality of mountingbosses 164, each of which defines a mounting fastener-receiving opening166 configured to receive a mounting fastener (not shown).

Furthermore, in a preferred embodiment and as best shown in FIGS. 2, 4,9, and 12, the mounting flange 162 in part defines the electronicscompartment 152 (in cooperation with the central body portion 155) anddefines a plurality of wire routing slots 168 providing access to theelectronics compartment 152.

A shaft opening 170 (see FIGS. 3 and 19) enables the routing of aharness or other electrical connectors (not shown) to the motorelectronics 154 through the shaft 34.

The covering 30 is preferably at least substantially rigid. Morespecifically, the covering is preferably formed of plastic or anothersuitable synthetic resin material that fixedly supports the core 28, thecoils 32, and the electronics 154 on the shaft 34. More particularly,the base 155 b of the central body portion 155 preferably defines ashaft-receiving opening 155 c. The shaft 34 is received in the opening.

Various means of shaft interconnection are permissible within the ambitof the present invention. The shaft might be press-fit or molded intothe opening for instance, or a separate coupling element might beprovided.

Preferably, a plurality of clip rings 169 a and at least one washer 169b are provided on the shaft 34 to restrict axial shifting of the stator18 and the rotor 20 relative to the shaft 34. More particularly, cliprings 169 a are preferably provided immediately above and below the base155 b of the body portion 155 of the covering 30 and above the bearingassembly 136. A washer 169 b is preferably provided above the bearingassembly 136, between the bearing assembly 136 and the corresponding oneof the clip rings 169 a.

Overmolding of Stator Core

As shown in FIGS. 5-8 and 13, in a preferred embodiment, theelectrically insulative covering 30 is overmolded onto the core 28 usinga mold 172. It is noted that, for the sake of clarity, the mold 172 isshown only schematically. That is, as will be readily understood by oneof ordinary skill in the art, components non-essential to the disclosurethe invention (e.g., hoppers, heaters, nozzles, etc.) are omitted; andthose components that are essential to disclosure of the invention maybe illustrated in a simplified form

The mold 172 preferably includes an upper cavity-defining portion 174and a lower cavity-defining portion 176. At least one of the uppercavity-defining portion 174 and the lower cavity-defining portion 176 ispreferably moveable, such that the mold 172 is configurable between anopen position as shown in FIGS. 6 and 7, and a closed position, as shownin FIGS. 5, 8, and 13.

The upper and lower cavity-defining portions 174 and 176 generallydefine a cavity 178 therebetween when the mold 172 is in the closedposition. Preferably, the cavity 178 corresponds to the core 28 of thestator 18 and, as shown in FIG. 8, receives the core 28 therein duringthe overmolding process.

More particularly, the cavity 178 preferably defines an axiscorresponding to an axis of the core 28. Furthermore, the cavity 178preferably includes a generally arcuate yoke region 178 a and aplurality of arcuately spaced apart tooth regions 178 b extendinggenerally radially from the yoke region 178 a. The yoke region 178 apreferably corresponds to the yoke 84 of the core 28, while the toothregions 178 b preferably correspond to the teeth 86 of the core 28.During the overmolding process, the yoke 84 is received in the yokeregion 178 a, and the teeth 86 are received in corresponding ones of thetooth regions 178 b.

The cavity 178 further preferably includes an accommodation region 180,best shown in FIG. 13, configured to accommodate variations in the axialheight of the core 28. For instance, the accommodation region 180 isconfigured to accommodate variations in stack height (i.e., axialheight) of the core 28 that can occur due to the accumulation of smalldeviations from the ideal thickness of the laminations of the core 28.

The axial covering thickness in the accommodation region 180 ispreferably less than about five (5) mm, although the actual thicknesswill depend on the core stack height (i.e., the axial height of the core28). In the most preferred embodiment, the stack height of the core 28is such that the covering has a thickness of about one (1) mm along theend faces 106 and 108 adjacent the teeth 86. Therefore, with thepreferred core height of about fifteen (15) mm, the preferred wiringthickness of about two (2) mm, and the preferred covering thickness ofabout one (1) mm, the stator 18 preferably presents a maximum height ofapproximately twenty-one (21) mm, as defined along the teeth 86 of thecore 28.

In a preferred embodiment, each of a plurality of arcuately spaced apartupper pins 182 extends generally axially toward the lowercavity-defining portion 176, while each of a corresponding plurality ofarcuately spaced apart lower pins 184 extends generally axially towardthe upper cavity-defining portion 176. The upper and lower pins 182 and184 extend in part into the cavity 178 when the mold 172 is in theclosed position to cooperatively at least in part secure the core 28 inthe cavity.

More particularly, as best shown in FIGS. 8 and 13, the upper and lowerpins 182 and 184 each preferably engage respective ones of the upper andlower faces 106 and 108 of the core 28. Corresponding pairs of the upperand lower pins 182 and 184 are preferably at least substantially axiallyaligned and, upon engagement of the core 28, cooperatively apply anaxially compressive load thereto. Axial movement of the core 28 isthereby at least substantially restricted.

Engagement of the upper and lower pins 182 and 184 with the core 28causes the formation of the previously described upper and lower toothopenings 132 and 134, respectively, in the covering 30.

The upper and lower cavity-defining portions 174 and 176 preferablydefine a radially outermost cavity margin 186 corresponding to the firstradial margin 96 of the core 28. Each of the upper and lower pins 182and 184 includes a respective radially innermost portion 188 or 190 thatis at least in part positioned radially inside the radially outermostcavity margin 186.

The positioning of the radially innermost portions 188 and 190 radiallyinside the radially outermost cavity margin 186 causes the formation ofthe previously described notches 136 in the covering 30. Preferably thepins 182 and 184 are circular in cross-section, such that, as describedabove, the notches 136 have a semi-circular shape.

Although the axial alignment of the upper and lower pins 182 and 184,their correspondence with each tooth 86, and the other configurationdetails described above are preferred, alternative arrangements of theupper and lower pins are permissible according to some aspects of thepresent invention. Such alternative arrangements correspond to thosediscussed in greater detail above with respect to the upper and lowertooth openings 132 and 134.

In a preferred embodiment, the upper pins 182 are axially fixed when themold 172 is in the closed position. More particularly, each of the upperpins 182 presents an endmost margin 192. The endmost margins 192cooperatively define a fixed, generally radially extending plane.

In contrast, the lower pins 184 are preferably axially moveable when themold 172 is in the closed position. More particularly, the lower pins184 are preferably biased toward the upper cavity-defining portion 174when the mold 172 is in the closed position. Such biasing enhances theability of the pins 182 and 184 to cooperatively axially compress andsecure the core 28 while accommodating minor variations in its axialheight due, for instance, to stacked tolerances associated with thelaminations of the core. (It is noted that the principles of theinventive mold are not limited to use solely with laminated cores.)

It is also permissible according to some aspects of the presentinvention for the upper pins to be biased in addition to or instead ofthe lower pins or for neither set of pins to be biased.

In a preferred embodiment, the mold 172 includes a plurality of springassemblies 194 each corresponding to one of the lower pins 184. As bestshown in FIGS. 6, 7, 8, and 13, each spring assembly 194 includes aspring 196, a spring block 198, and a block fastener 200 removablysecuring the block 198 to the lower cavity-defining portion 176 of themold 172. As will be described in greater detail below, each spring 196is preferably positioned below a corresponding lower pin 184 to bias thelower pin 184 toward the upper cavity-defining portion 174. Alternativebiasing means are permissible without departing from the scope of someaspects of the present invention, however.

As described in more detail below, the spring block 198 generally servesto guide, support, and secure the corresponding lower pin 184 as itshifts under the influence of the corresponding spring 196.

More particularly, each lower pin 184 preferably includes a distal end202 spaced away from the core 28 and a proximal end 204 adjacent thecore 28. The distal end 202 preferably includes an enlarged head 206 ofthe lower pin 184.

Furthermore, the spring block 198 preferably includes a distal recess208 for receiving the corresponding spring 196, the head 206, and aleast a portion of the distal end 202 of the corresponding lower pin184. (The degree to which the distal end 202 is received in the distalrecess 208 will vary according to the degree of extension of the spring196.) The spring block 198 further preferably includes a proximal recess210 for receiving the proximal end 204 and potentially a portion of thedistal end 202 of the lower pin 184. (The degree to which the distal end202 is received in the proximal recess 208 will vary according to thedegree of extension of the spring 196.)

A spring block shoulder 212 is defined between the distal and proximalrecesses 208 and 210, respectively. The spring block shoulder 212preferably restricts the axially upward shifting of the correspondinglower pin 184 by engaging the head 206 of the corresponding lower pin184.

In a preferred embodiment, the mold 172 further comprises a plurality ofinner pins 214 extending at least in part through the core 28 to atleast substantially restrict radial shifting of the core 28. Mostpreferably, the inner pins 214 extend at least substantially axiallythrough the entirety of the core 28.

Preferably, each of the inner pins 214 corresponds to the yoke 84 of thecore 28 and the yoke portion 120 of the covering 30. More particularly,when the mold 172 is in the closed position, the inner pins 214 extendthrough the previously described yoke openings 142. The presence of theinner pins 214 in such a position results in the formation of theaforementioned upper and lower yoke holes 138 and 140.

Preferably, each of the inner pins 214 presents a generally radiallyextending shoulder 216 defined between an wide region 218 and a narrowregion 220 of the corresponding inner pin 214. As best shown in FIG. 13,the narrow region 220 of each inner pin 214 preferably extends into thecorresponding one of the yoke openings 142, while the shoulder 216engages the core 28 and restricts axial movement of the respective innerpin 214 relative to the core 28. The region in which the shoulder 216engages the core remains uncovered by the covering 30, as noted above.

The wide region 218 of each inner pin 214 is preferably threaded throughthe upper cavity-defining portion 174.

Although the above-described configuration is preferred, it is withinthe scope of some aspects of the present invention, however, for theinner pins to be alternatively configured. Among other things, forinstance, the inner pins might have constant cross-sections, be devoidof threading, and/or be inserted through the lower cavity-definingportion.

High Efficiency Power Supply Design

As noted previously, the fan 12 of the present invention preferablyincludes a highly efficient power supply. More particularly, asillustrated in FIGS. 20-22, the fan 12 preferably includes a motorcontrol 222 (part of the previously described motor electronics 154) forcontrolling the motor 14.

The motor 14 may be, for example, a three-phase motor such as athree-phase wye-connected brushless DC permanent magnet motor. However,other motors may be used with the motor control described herein withoutdeparting from the scope of the invention.

The motor control 222 may comprise a controller 224, level shifters 226,drivers 228, sensors 230, and a high-efficiency power supply 232. Thecontroller 224 may be a microcontroller, microprocessor, or the likeconfigured to send and receive control signals for controllingoperational characteristics of the motor 14. In some embodiments of theinvention, the controller 224 may be configured to operate at lowervoltages than the motor 14. For example, the controller 224 may beoperated at three and three tenths (3.3) volts (V) while the drivers 228and/or the motor 14 may be driven at twelve (12) to twenty-four (24) V.The controller 224 may comprise a programming port (not shown) forinitially receiving computer-readable instructions and/or softwareupdates, and may also comprise a user interface port (not shown) forreceiving commands from a user, such as by way of a customer optionboard, switches, dials, buttons, or any other user interfaces known inthe art.

The level shifters 226 may include three motor phase level shifterselectrically coupled between the controller 224 and the drivers 228 ofthe motor control 222, creating an interface between the low voltagedomain of the controller 224 and the higher voltage domain of thedrivers 228. The level shifters 226 may also be configured to operate atlower voltages than the motor 14. For example, the level shifters 226may be operated at five and five-tenths (5.5) V while the drivers 228and/or the motor 14 may be driven at twelve (12) to twenty-four (24) V.In some embodiments of the invention, the level shifters 226 maycomprise a motor phase “U” level shifter, a motor phase “V” levelshifter and a motor phase “W” level shifter, as illustrated in FIG. 21.

The drivers 228 may be electrically coupled between the level shifters226 and the motor 14. Specifically, there may be three drivers 228electrically coupled to provide three phase voltage to the motor 14. Insome embodiments of the invention, the drivers 228 are dual MOSFETdrivers. However, other drivers known in the art may be used withoutdeparting from the scope of the invention.

The sensors 230 may comprise current sensors electrically coupledbetween the drivers 228 and the controller 224 and may be configured toprovide feedback to the controller 224. This sensed current may be usedby the controller 224 to sense any errors or overload situations and totake corrective or protective action accordingly.

The high efficiency power supply 232 described herein may be configuredto increase fan efficiency at all rated speeds. Specifically, the highefficiency power supply 232 is configured to decrease input power from ahigher voltage to a lower voltage. The higher voltage may still be usedto drive the motor 14 and/or drivers 228 thereof, as illustrated in FIG.20, but other components of the motor control 222, such as the levelshifters 226 and various other switching components, may be operated bythe lower voltage, thus keeping switching losses lower than traditionalmotor power supplies.

The high efficiency power supply 232 may be any power supply configuredto drop a first input voltage 234, received from an external powersource, to a second lower voltage 236. For example, as illustrated inFIGS. 20-22, the high efficiency power supply may comprise a step-downbuck converter 238 and a low drop-out voltage regulator 240.Additionally or alternatively, the buck converter 238 or voltageregulator 240 may be replaced with a switching regulator or a step-downvery low drop out linear regulator without departing from the scope ofthe invention. The step-down buck converter 238 may output the secondlower voltage 236 for driving the level shifters 226, while the lowdrop-out voltage regulator 240 may output a third lowest voltage 242 fordriving the controller 224, as illustrated in FIG. 20. The third lowestvoltage 242 may be less than the second lower voltage 236. However, insome embodiments of the invention, the controller 224 may be driven bythe second lower voltage 236 output by the step-down buck converter 238,and the low drop-out voltage regulator 240 may be omitted withoutdeparting from the scope of the invention.

The external power source may be accessed via an electrical outlet orany other input power connections known in the art. For instance, theexternal power source may include or couple to the aforementionedconverter (not shown) that converts 100-240 VAC to 12-24 VDC. Thus, in apreferred embodiment, the first input voltage 234 may be, for example,twelve (12) V or twenty-four (24) V, and the second lower voltage 236may be in the range of five (5) V to six (6) V. However, any first inputvoltage 234 may be reduced to any second lower voltage 236 depending onthe configuration of the high efficiency power supply 232. For example,the second lower voltage 236 could be in the range of four (4) V to nine(9) V. A lower limit to the second lower voltage 236 may be determinedbased on the minimum switching voltage required by switching componentsor the level shifters 226 of the motor control 222. The third lowestvoltage 242 may be, for example, in the range of three (3) V to four (4)V. However, the third lowest voltage 242 may be set to any voltagesufficient to drive the controller 224 without departing from the scopeof the invention.

In some embodiments of the invention, as illustrated in FIG. 21, thehigh efficiency power supply 232 may further comprise noise filteringcircuitry 244, bulk energy storage circuitry 246, other variousfiltering and energy storage circuitry, and/or a compensation network248. The noise filtering and bulk energy storage circuitry 244 and 246,respectively, as illustrated in FIGS. 21-22, may comprise variouscapacitors arranged in parallel with each other and/or any otherconfigurations known in the art. Notice that filtering and energystorage may occur before and after the buck converter 238 and voltageregulator 240, as illustrated in FIGS. 21-22.

Motor Performance

The fan 12 is preferably configured to achieve low-speed efficiencies ofat least about fifty percent (50%) and high-speed efficiencies of atleast about seventy percent (70%). For instance, FIG. 23 presents testdata associated with a motor suitable for use in the preferred fanembodiment of the present invention. The data is provided for speedsranging from seventy (70) to two hundred one (201) revolutions perminute (rpm), which correspond to torques from one tenth (0.100) to one(1.000) Newton-meter (N-m) and power usages from one and forty-threehundredths (1.43) to twenty-nine and fifty-six hundredths (29.56) Watts(W). Efficiencies corresponding to these parameters range from fifty-oneand three tenths percent (51.3%) to seventy-one and two tenths percent(71.2%).

CONCLUSION

Although the above description presents features of preferredembodiments of the present invention, other preferred embodiments mayalso be created in keeping with the principles of the invention.Furthermore, these other preferred embodiments may in some instances berealized through a combination of features compatible for use togetherdespite having been presented independently in the above description.

The preferred forms of the invention described above are to be used asillustration only and should not be utilized in a limiting sense ininterpreting the scope of the present invention. Obvious modificationsto the exemplary embodiments, as hereinabove set forth, could be readilymade by those skilled in the art without departing from the spirit ofthe present invention.

The inventors hereby state their intent to rely on the Doctrine ofEquivalents to determine and assess the reasonably fair scope of thepresent invention as pertains to any apparatus not materially departingfrom but outside the literal scope of the invention set forth in thefollowing claims.

What is claimed is:
 1. An electric motor comprising: a stator; a rotorrotatable relative to the stator about an axis; and a bearing rotatablysupporting the rotor, said rotor including a backing ring, a diecastrotor can, and a plurality of arcuately arranged magnets, said rotor canincluding a non-machined sidewall and a radially extending base plate,said sidewall being diecast integrally as part of the rotor can andprojecting axially from the base plate, said rotor can defining abearing pocket in which the bearing is at least partially received, saidsidewall extending about the axis to define an interior can space, saidbearing pocket being at least in part outside the interior can space,said rotor can being diecast in an overlying relationship with at leastpart of the backing ring, with the sidewall and backing ring beingsecurely interengaged so as to restrict relative shifting therebetween,said backing ring including a pair of axially spaced apart end faces,each of which extends outwardly relative to the axis, and a pair ofradially spaced apart, oppositely directed inner and outer faces, theplurality of arcuately arranged magnets being fixed adjacent one of theinner and outer faces, the other of said inner and outer faces beingdevoid of machining and abuttingly engaging the sidewall of the rotorcan, said backing ring being concentric with said bearing pocket, saidbacking ring and said rotor can comprising dissimilar materials, saidsidewall including a pair of axially spaced apart non-machined, diecastshoulder portions, said shoulder portions abutting respective ones ofthe end faces to thereby axially capture the backing ring therebetween.2. The motor of claim 1, said backing ring presenting a side face thatextends axially between the end faces, with each end face beingnon-parallel to the side face, said sidewall including a non-machined,diecast axial portion that abuts the side face of the backing ring. 3.The motor of claim 1, said sidewall having a toroidal shape, saidsidewall being continuous.
 4. The motor of claim 1, each of said endfaces extending between the inner and outer faces.
 5. The motor of claim1, said magnets being mounted to the inner face, said motor being anouter rotor motor such that the backing ring and the magnetscircumscribe the stator.
 6. The motor of claim 1, said backing ring andsaid bearing pocket being concentric.
 7. The motor of claim 1, saidbacking ring having a radial thickness of 3 mm, said sidewall having anouter diameter of 185 mm.
 8. The motor of claim 1, said sidewall furtherdefining an inner shoulder spaced radially inwardly from at least one ofsaid shoulder portions, said inner shoulder further being spaced axiallyfrom said at least one of said shoulder portions.
 9. The motor of claim8, a first one of said shoulder portions being disposed between saidinner shoulder and a second one of said shoulder portions.
 10. The motorof claim 9, said rotor can defining an annular groove between said innershoulder and said at least one of said shoulder portions.
 11. Anelectric fan comprising: a plurality of blades; and an electric motorfor rotating the blades, said electric motor including— a stator, arotor rotatable relative to the stator about an axis, and a bearingrotatably supporting the rotor, said rotor including a backing ring, adiecast rotor can, and a plurality of arcuately arranged magnets, saidrotor can including a non-machined sidewall and a radially extendingbase plate, said sidewall being diecast integrally as part of the rotorcan and projecting axially from the base plate, said rotor can defininga bearing pocket in which the bearing is at least partially received,said sidewall extending about the axis to define an interior can space,said bearing pocket being at least in part outside the interior canspace, said rotor can being diecast in an overlying relationship with atleast part of the backing ring, with the sidewall and backing ring beingsecurely interengaged so as to restrict relative shifting therebetween,said backing ring presenting a pair of axially spaced apart end faces,each of which extends outwardly relative to the axis, and a pair ofradially spaced apart, oppositely directed inner and outer faces, theplurality of arcuately arranged magnets being fixed adjacent one of theinner and outer faces, the other of said inner and outer faces beingdevoid of machining and abuttingly engaging the sidewall of the rotorcan, said backing ring being concentric with said bearing pocket, saidbacking ring and said rotor can comprising dissimilar materials, saidsidewall including a pair of axially spaced apart non-machined, diecastshoulder portions, said shoulder portions abutting respective ones ofthe end faces to thereby axially capture the backing ring therebetween.12. The electric fan of claim 11, said backing ring presenting a sideface that extends axially between the end faces, with each end facebeing non-parallel to the side face, said sidewall including anon-machined, diecast axial portion that abuts the side face of thebacking ring.
 13. The electric fan of claim 11, said sidewall having atoroidal shape, said sidewall being continuous.
 14. The electric fan ofclaim 11, said end faces extending between the inner and outer faces.15. The electric fan of claim 11, said magnets being mounted to theinner face, said motor being an outer rotor motor such that the backingring and the magnets circumscribe the stator.
 16. The electric fan ofclaim 11, said blades being fixed to the rotor can for rotationalmovement therewith about the axis.
 17. The electric fan of claim 16,said rotor can including a plurality of mounting brackets projectingradially from the sidewall, said blades being connected to the mountingbrackets.
 18. The electric fan of claim 11, said backing ring and saidbearing pocket being concentric.
 19. The electric fan of claim 11, saidbacking ring having a radial thickness of 3 mm, said sidewall having anouter diameter of 185 mm.
 20. The motor of claim 11, sidewall furtherdefining an inner shoulder spaced radially inwardly from at least one ofsaid shoulder portions, said inner shoulder further being spaced axiallyfrom said at least one of said shoulder portions.
 21. The motor of claim20, a first one of said shoulder portions being disposed between saidinner shoulder and a second one of said shoulder portions.
 22. The motorof claim 21, said rotor can defining an annular groove between saidinner shoulder and said at least one of said shoulder portions.